16 Network Geographic Information System

Information System (GIS) has been well established as an information system for acquiring, storing, processing, analyzing and visualizing spatial data. The success of GIS is reflected from the following developments: (1) numerous GIS software have been developed and are widely used; (2) A large amount of spatial datasets have been collected and used; (3) Many books and papers have been written to introduce and discuss different aspects of GIS. They range from providing an However, relevant problems also arise: (1) Different software companies, such as ESRI (www.esri.com) and Intergraph (www.imgs.com), developed their own software with full GIS functions, and sold their software at a fully functional price. However, most customers just use the mapping function which accounts for no more than 30% of the full GIS functions, and almost no software are used all the time. (2) A large number of spatial databases are constructed from national level (such as NASA and USGS), state level (such as Virginia and Maryland), to county level (such as Fairfax and Loudoun). National applications (such as Homeland Security) call for full integration of these spatially dispersed databases. To save the investment on GIS nationally and internationally requires sharing and connecting spatial data and software. (3) While current literatures focus on using existing software for application research, GIS basic functions need to be revisited (Wise, 2002) for building new software platforms for sharing spatial data and processing (Yang et al., 2002). Fortunately, the emerging and fast development of computer networks, especially WWW and the Internet, provide a communication framework to solve these problems. The marriage of GIS and computer networks has produced many To integrate GIS among networks for sharing the data and software, scholars propose many new architec-tures, such as agent-based GIS (Luo, 1999), distributed geospatial information